1D - Organs and Tissues of the Immune System

Question 1

bone marrow

Answer 1

Primary site of blood cell production in adults

Question 2

red blood cells

Answer 2

(erythrocytes) - carry oxygen and are important in cellular respiration

Question 3

white blood cells

Answer 3

(leukocytes) - important mediators and participants of both the innate and adaptive immune response

Question 4

formation and maturation of B and T lymphocytes

Answer 4

formation in the bone marrow lymphocytes mature and differentiate
• T-lymphocytes migrate to the thymus
• In Avian species B-Lymphocytes migrate to the Bursa of Fabricius
• Mammals do not have a Bursa so B-lymphocytes continue to mature in the bone marrow
‣ Mature lymphocytes migrate to the secondary lymphoid tissues such as the lymph nodes, spleen and mucosal associated lymphoid tissues to conduct surveillance and respond antigenic stimuli

Question 5

secondary lymphoid tissues

Answer 5

Thymus, Bursa of Fabricius, Spleen

Question 6

thymus presence

Answer 6

present in young animals
◦ Located cranial to the heart
◦ Undergoes involution around the time of puberty
◦ T-cells mature and differentiate here

Question 7

bursa of fabricius

Answer 7

◦ Only in birds
◦ Where B-cells mature and differentiate in birds
◦ B-cells mature and differentiate in the bone marrow in mammals

Question 8

lymphatic system major components

Answer 8

◦ Lymph nodes, spleen, lymph vessels

Question 9

lymphatic system flow

Answer 9

◦ Unidirectional flow
‣ Augments the circulatory system
‣ Drains extracellular fluid (lymph)
‣ Movement of lymph brings micro-organisms and other foreign substances into contact with the immune cells

Question 10

lymph

Answer 10

Fluid in the lymphatic vessels

Question 11

movement of lymph through the body

Answer 11

◦ Lymphatic vessels run parallel with the blood vessels
◦ Lymph returned to blood vessels via the lymphatic duct and the thoracic duct
◦ No pump - relies on movement and muscles
◦ On its return to the heart lymph is filtered at the lymph nodes

Question 12

edema

Answer 12

occurs when lymphatics are blocked or damaged or if fluid leaks out of the lmphatics faster than it moves in

Question 13

causes of edema

Answer 13

‣ Parasites and elephantiasis
• Eg Filariaisis
‣ Traumatic lymphatic damage
• Eg post surgery (breast cancer → mastectomy)
‣ Removal of lymph nodes
‣ Eating too much salt followed by inactivity

Question 14

lymph nodes

Answer 14

can be found throughout the body
◦ Full of lymphocytes and some other immune cells surrounded by fibrous capsule
◦ involved in immune system activation
◦ Enlarge in response to foreign substances

Question 15

spleen

Answer 15

◦ Very vascular lymphoid organ attached to the stomach

◦ Made up of red pulp and white pulp

Question 16

red pulp

Answer 16

splenic cords and vascular spaces are filled with RBC and macrophages
• Macrophages removes old and sick red blood cells

Question 17

white pulp

Answer 17

splenic follicles) filled B cells and are surrounded by T-cells

Question 18

tonsils

Answer 18

◦ Un-encapsulated aggregations of lymphoid tissue in the pharynx
‣ No afferent vessels
‣ Have direct contact with the foreign substances (eg route of entry for Parvo virus in dogs

Question 19

MALT

Answer 19

Mucosa Associated Lymphoid Tissues)
◦ The first line of defense at the mucosal barrier
◦ Sentinel stations for the immune system

Question 20

sentinel stations for the immune system

Answer 20

‣ BALT - Bronchial Associated
‣ GALT - Gastro-intestinal tract, Peyer’s Patches
‣ Also in the urogenital tract

Question 21

M-cells

Answer 21

◦ Specialized epithelial cells that are located over the Peyer’s patches in the intestine
‣ M = Microfold cell
‣ M-cells help deliver antigens across the epithelium to the Peyer’s patches
◦ also a site of entry for pathogenic micro-organisms such as Yersinia, Salmonella, Rhodococcus, and some viruses such as BVDV